Telephone transmitter



Mams@ JuneZ, 1923. v

` R. L. MURRAY TELEPHONE TRANSMITTER Filed Aug. 24, 1921 m mmwlll,

Patented .lune 2%, 1923.

'Uldlfll STA-l@ ROBERT LAMBERT MURRAY, OF BUSHEY HEATH, ENGLAND, ASSIGNOR TO TELEPHONE i MANUFACTURING COMPANY LIMITED, OF LONDON, ENGLAND.

TELEPHONE TRANSMITTER.

Application led August 24,- 1921. Serial No. 494,771.

To all whom t may concern.'

Be it known tha't I, ROBERT LAMBERT MUR- RAY, a subjectof the vKing of England, re-

siding in Bus-hey Heath, I-lfertfordshire, 5 England, have invented certa-in new and useful Improvei'nents in Telephone Transmitters, of which the following is a specification.

This invention relates'primarily to telephone transmitters or that type vin which' the diaphragm or a pad thereon is intended to be held in contact .with a surface of portion of the users person, hereinafter referred to in a general way as the throat', in contradistinction to the type intended to beheld near the mouth to receive sound transmitted. through the air. The term pad is intended to denote any projecting part carried upon the diaphragm itself so as to be. situated lbetween the diaphragm and the surface against which it is tov be pressed so that vibrations are transmitted to the diaphragm mechanically and directly through the said projecting part, irrespective of any that may be transmitted through the air also. i

The object of the present invention is to provide al construction of transmitter of the aforesaid type which shall be better adapted for application to the users throat than those heretofore constructed, and which moreover shall be less liable than are transmitters of the ordinary construction, to become momentarily ino erative owing to the position inwhich it is eing held.

According to the present invention there is provided inca telephone transmitter, the combination with a support, and a microphone comprising a. fixed element carried 40 by the support and a movable' element arranged to coeoperate with the fixed element, of a diaphragm that is domed so as to present an external convex surface and is secured solely at its circumferential margin to said support, which diaphragm is provided with an integral central boss, to which the said movable element of the microphoneis secured. w

Preferably the boss is of a diameter not exceeding three-,quarters of the diameter of that portion of the diaphragm which is com prised within: the circumferential margin' 'that serves to connect it to itsl support, in

-tion 12, and .whereo order that the dia hragm may have the Other features of the invention will be described hereinafter and pointed outv in the claims.

The embodiments of this invention shown in the accompanying drawings serve further to illustrate the nature of the invention. In the drawings l 'Figure 1 is a central section through one construction of transmitter according to this invention7 Figure 2 is a similar View of an alternative construction, and

Figure 3 vis a detail sectional view, similar to Fig. 1, illustrating a further modification.

The transmitter 1 is built, together with a receiver 2, upon a foundation ring 3 comis encircled bythe ring and* is mounted upon a base-plate 5 by screws (not shown) passing through the magnet and into the base late. The solenoid coresI of the magnet are -shaped and have each one limb gripped between the magnet ring 11 and the base plate. The base plate 5 yserves to close one otherwise open side ofthe ring, and the other open side is closed by the receiver diaphragm 6 which is. covered byl a dished flanged cap 7 whereof the flange 8 surrounds the ring and isjsecured to the latter by screws not shown. The concavity ofthe cap is towards the diaphragm and a duct 9 On .the opposites'ide of the base-plate 5 to that on which the receiver magnet is mountmon to them both. The receiver magnet 4 v leads from the chamber thus formed between `the diaphragm and the cap to thethe ear pieces.

ed, is a carbon' disc 10 vconductingly attached v to the plate., A transmitter diaphragm 11 Vis prepared in the form of a cup-like cap cylindrical body porthe lip has an externally .directed radial flange 13 and fromthe centre of the bottom whereof springs a Small cylindrical boss 15 integral with the having a substantially diaphragm and cap as it may be described, is made in one p-iece of ebonite. Upon the boss 15 is mounted 'a carbon cup 14whose open mouth is directed towards the disc 10.

A metallic securing ring 16 is provided for the combined diaphragmrand cap, arranged to encircle the foundation ring 3 and'pr vided with 'a `small inwardly directed flange 17 to engage the flange upon the lip 13. The

diaphragm. This diaphragm, or combined y securing ring 16 is made fast in any convenient way to the foundation ring.

The carbon cup is charged with carbon shot or granules 18, and, when the parts are assembled, is closed, and the granules thereby retained in position, by the disc 10.

Connection is made to the carbon cup 14 by an insulated wire 19 passing from a metallic washer 20 through a hole 21 'in the' foundation 5, although this portion of the wire 19 is omitted for the sake of clearness. Its end within the receiver is, together with the necessary connections for the receiver magnet winding, connected in the usual manner' tov a multiple way flexible cable 22 serving to complete the circuit in any convenient way with the remainder of the telephone system. The connection to the fixed element 10 of the microphone is notshown, but preferably consists of a strand of the cable 22 connected in any convenient manner to the ring 4 which is in electrical connection with the carbon disc 10. l

Two alternative constiuctions with regard to further detail are shownrm Figures '1 and 8.

As shown inF'igure 1, screws 23, four in number, are arranged to project from the washer 24 and a washer 25 of resilient mate-'7 rial, such as rubber, are interposed.

The function of the screws is to enable the working distance between the disc 10 and cup 14 to be adjusted, while the functiorrof the re. silient washer 25 is to enable the degree of rigidity with which the diaphragm is held at its circumference to be varied by the consequent variation in the degree 'of compres sion applied by the securing ring 16 to the Washer. l In the construction indicated in Figure 3, the screws 23 and washers 24 and 25 are re-. laced by a resilient metallic washer, such for example as an ordinary spring` washer 2G.

The construction shown in Figure 2 is similar to that shown in Figure 1 in its general features. but differs in detail as is necessitated partly by the fact that it is not mounted to constitute an unitary device with a receiver. Thus, for example, the foundation ring 3 andbase-plate 5 are replaced by the dished stamping 27 of metal upon which the disc 10 is insulatingly supported and held` by a screwed stem 28, insulated, as shown, from the stamping 27. In this construction, as well as in that shown in Figure 1, the cup 14 is secured to the boss bya screw 29 whose tip does not, however, pass to the outer surface of the diaphragm 11. The hole for it may, however, be drilled clear throughand the outer end subsequently plugged in any convenient income recte'd radial flanges is in the ,form of pliable lugs which vmay readily be bent over and form in effect a mutilated flange.

The substance of thediaphragin, as will readily be understood, is made as thin as practicable over the majority of the surface lying between the outer margin andthe cent-re but is of course thickened at the j centre by `thepresence of the aforesaid boss. l' It may also bethickened near the margin as indicated in 'chain line at 110 in Figure 2, by being formed with an annular projection so that the resilience of the support afforded to the carbon cup resides principally in portion 112 of the diaphragm lying between the saidannular thickening and the boss.

Instead of the diaphragm being formed with a cylindrical body or extensionthat is flanged, the flange may be omitted and the diaphragm secured by 4its body alone, or again alternatively the cylindrical portion may 'be absentl and the diaphragm merge imperbeptibly into the flange which may be held by lthe securing ring as above described. Furthermore, although the diaphragm is above described as being made of- 'non-conducting material, it may be made of metal, if preferred, and it may, if desired, not be made entirely in one piece whether of .metal or not.

What I claima-s my invention and desire 1. In al telephone transmitter, a support,

a microphone comprising a fxedgelementcarried by the support and a movable ele`- ment arranged to co-operate with the fixed element, a resilientcompression member lcarried by said support, a flexible diaphragm l the diaphragm comprised within its circumferential margin, and clamping means carried by said -support and arrangedto clamp the circumferential portion of said diaphragm against said resilient member.

v2. lIna telephone transmitter, a support,

a microphone comprising a fixed element in the form of a disc carried by the support and a movable element comprising a cup-shaped memberhaving carbon granules therein ar- Macnee ranged to co-operate with the fixed element, a

a diaphragm domed to prsent an external convex surface, said diaphragm beingsecured solely at its circumferential margin to said support, and provided with an integral central boss to which said cup-shaped element is attached with its open month directed towards but spaced away from said fixed element.

3. ln a telephone transmitter, asnpport, a microphone comprising a fixed element in the form of a disc carried by the support and a movable element comprising a cupshaped member having 'carbon granules therein arranged to co-operate with the fixed element, a resilient compression member carried by vsaid support, a exible diaphragm supported by its. circumferential portion on ysaid resilient member., said Y erential portion of said diaphragm against said resilient member. l

In testimony whereof l affix myv signature,

soenna LAMBERT MURRAY( Witnesses:

'L GnmsNAomi, T, el'. Osman. 

